Corrosion preventing agent



No Drawing. Application May 19, 1955 Serial No. 509,675

Claims. (Cl. 252-46.6)

assignor to Esso a corporation of The present invention relates to the improvement of hydrocarbon products derived from petroleum sources and more particularly to the preparation of improved mineral lubricating oil compositions by the incorporation therein of a new class of additives which impart improved properties to such hydrocarbon products.

This application is a continuation-in-part of patent application Serial No. 192,617, filed on October 27, 1950, now abandoned.

In the development of petroleum lurbicating oils the trend has been to use more and more efiicient refining methods in order to reduce the tendency of the oils to form carbon and deposits of solid matter or sludge. While such highly refined oils possess many advantages, their resistance to oxidation, particularly under conditions of severe service, is generally decreased and they are more prone to form soluble acidic oxidation products which are corrosive. They are generally less effective than the untreated oils in protecting the metal surfaces which contact against rusting and corrosion due to oxygen and moisture. Although generally superior to lightly refined oils they may deposit films of varnish on hot metal surfaces, such as the pistons of internal combustion engines, under very severe engine operating conditions.

In accordance with the present invention a new class of products has been discovered which when added to refined lubricating oils in small proportions substantially reduce the tendency of such oils to corrode metal surfaces, and which are particularly effective in inhibiting the corrosion of copper-lead and cadmium-silver bearings. They are likewise effective in inhibiting oxidation of such oils and other petroleum hydrocarbon products, as will be more fully explained hereinafter.

The new class of materials which have been found to possess the antioxidant and stabilizing qualities described above are the condensation products of epoxides with the reaction products of phenol sulfides and phosphorus pentasulfide. It is believed that the condensation product formed in accordance with this invention is predominantly a compound of the formula:

where R is an aromatic or aliphatic-aromatic hydrocarbon radical, x is an integer of l to 2; and where 'one of the symbols R R R and R represent a hydrogen atom, an aliphatic hydrocarbon radical containing 1 to 4 carbon atoms or a phenyl radical and the others of the symbols R R R and R represent hydrogen atoms. Preferably one of the symbols R R R and Rgrepresents an aliphatic hydrocarbon radical containing 1 to 4 carbon atoms or a phenyl group and the others represent hydrogen atoms.

The phenol sulfides which may be reacted with phos- 2,826,556 Patented Mar. 1958 where R is a hydrogen atom or an alkyl radical. The preferred phenol sulfides are alkyl phenol sulfides containing 4 to 24 or more carbon atoms in each alkyl group. Particularly preferred alkyl phenol sulfides contain 6 to 12 carbon atoms in the alkyl group attached to each of the two benzoid nuclei. The symbol x is an integer of 1 to 2. It is preferred that R contain at least 4 carbon atoms to provide a final additive product which has good oil solubility. The preparation of these phenol sulfides is well known in the art and is described in detail for example in U. S. 2,518,379 (column 4, lines 8-53). Specific examples of these phenol sulfides include tert. octyl phenol sulfide, nonyl phenol sulfide, amyl phenol sulfide, cetyl phenol sulfide, etc. These are prepared preferably by reacting sulfur chloride with the particular alkyl phenol.

The reaction between the phenol sulfide and phosphorus pentasulfide is carried out using approximately the same reaction conditions which are well known in the art for preparing dithiophosphoric acids from alcohols and phosphorus pentasulfide. However, in the present reaction about 2 moles of phenol sulfide are reacted with one mole of P 8 to form a product believed to be predominantly (Dithiophosphoric acid) This reaction is carried out at a temperature of about to 175 C., preferably about to C. by stirring the reactants together until the P 8 has been consumed. This can be noted visually. The reaction time required will generally be in the range of about 0.5 to 5 hours, usually about 1 to 2 hours. After the reaction is completed the reaction product is preferably blown with nitrogen or other inert gas to remove hydrogen sulfide therefrom. If desired, the reaction may be carried out in a solvent such as a mineral oil, e. g., a mineral lubricating oil.

The epoxides which are condensed with the phenol sulfide-P S reaction products in accordance with this invention include especially the well-known alkylene oxides having 2 to 6 and preferably 3 to 4 carbon atoms per immediately upon contact of the reactants at normal room temperatures, and may be conveniently conducted by adding about one mole of the epoxide slowly to one mole of the dithiophosphoric acid while rapidly stirring the reaction mixture and controlling the temperature by means of a water or ice bath. Generally temperatures in the range of about 20 to 100 C. may be employed. No catalyst is required, and the time required for the completion of the reaction is not greater than two hours and is usually much less. Reaction times of about 0.2 to 2 hours may generally be employed. Solvents are not normally required, but in some cases it may be convenient to conduct the reaction in the presence of. well known inert solvents such as ethylenedichloride,.beuzene, xylene, or a mineral oil.

The amount of the additives of the present invention which is to be employed in mineral lubricating oil compositions or other petroleum hydrocarbon compositions (which about 0.02% to 5%, more generally from about 0.1 to about 2% by weight, based on the total composition, and the particular amount in individual cases will be selected in accordance with the requirements of the case and in view of the properties of the base stock employed. For commercial purposes, it is couvenienttoprepare concentrated oil solutions in which the amount of additive in the composition ranges from 25 to 5.0% by weight, and to transport and store them in such form. In' preparing a lubricating oil composition for use as a crankcaselubricant the additive concentrate is merely blended with the base oil in the required amount.

The preparation and testing of the additives of the present invention are illustrated'in the examplesdescribed below, but it is to be understood that the additives prepared and their application in various tests are illustrative only and are not to be construed as limiting. the scope of theinvention in any manner.

Example l.-Tert.-ctylphenyl' sulfide dithiophosphoric acid-butadiene monoxide reaction product A mixture of 460 g. (0.5 mol) of a 50% oil solution of tert'.-octylphenolsulfide (containing an. average of about 1.5 atoms of S for each pair of benzene rings')'an"d 55.5 g. (0.25 mol) of P 8 was heated at 145" C. for 1 hour with rapid stirring, followed by filtration and a 20-minute nitrogen blowing. period on the steam bath. The product was predominantly t'ert.-octylphenol sulfide dithiophosphoric acid.

The product was transferred to'a 4-necked 2-liter flask equipped with a stirrer, thermometer-,- dropping funnel, and reflux condenser. 35.0 g. (0.5 mol') of butadiene monoxide was added dropwise over a. period of 45 min-' utes, maintaining the temperatureibelow 45 C. by means of an ice bath. After stirring for this temperature, the product wason the steam bath. for 25- minutes. viscous liquid was. obtained which. analyzed 2.6% 'phos phorus and 9.4% sulfur.

Example 2.Tert'.-o'ctylphenyl' sulfide dithiophosphoric acid-styrene oxide reaction product Thev tert..-octylphenol sulfide prepared as described in Example 1'.

At a temperature of 45 C., 60 g. (.015 mol) of styrene oxide was added. to the thiophosphoric acid over a period of about 45 minutes with rapid stirring. After stirring for an additional hour at. this temperature, the product was placed on the steam bath and blown'wi'th nitrogen for 25 minutes. A clear, dark red, viscous liquid was obtained which analyzed 26% phosphorus and 818% sulfur. 1

Example 3.Nonylphenal sulfide dithiophosphoric acidpropylene oxide reaction product A mixture of 495 g'. (025 mol)" era 50% oil solution of nonylphenol sulfid (containing an average" of about 1.8- atomsof S foreachpair of benzene rings)" and 5515" g. (0.25 mol) of P 8; washeated at 150 for; 1 hour with rapid stirring; The product was then" filteredand blown with nitrogen on the stea-m batli for20 minutes.

an ice bath. Afterstirring for anadditional hour at anadditional hour, at blownwith nitrogen A clear, dark red,

dithiophosphoric acid was t each of the products of Examples 1 to 3 room temperature, the product was blown with nitrogen for about 25 minutes on the steam bath. A clear, dark red, viscous liquid was obtained which analyzed 2.1% P and 9.0% S.

Example 4.S. 0. D. corrosion test Blends were prepared containing 0.25% by weight of in a paraflinic mineral lubricating'oil of SAE 20 grade. Where the product was obtained in the form of a mineral oil solution a quantity of the product was employed which was equivalent to 0.25% of the active compound.

These blends and a sample of the unblended base oil were submitted to a corrosion test, known as the S. O. D. corrosion test, designed to measure the eifectiveness of the product in inhibiting the corrosiveness of a typical mineral lubricating oil toward the surfaces of copperlead bearings. The test was conducted as follows: 500 cc. of the oils' was placed ina glass oxidation tube (13 inches long and- 2% inches in diameter) fitted at the bottom with a /4- inch air inlet tube perforated to facilitate air distribution. The oxidation tube was then immersed in a heating. bath so that the oil temperature was maintained at 325 F. during. the test. Two quarter sections of. automotive bearings of copper-lead alloy of known weight having a total area of 25 sq. cm. were attached to opposite sides 05 a. stainless steel rod which was then immersed in the testoil. and rotated at 600 R. P. M., thus providing. sufiicient agitation of. the sample. during the test. Air was. then blown through the oil atthe rateof 2 cu. ft.-- per hour. At the end ofi each 44101 11 period the hearings were removed, washedwithnaphtha, andweighed to determine the amount of loss by corrosion. The bear-ings werethen repolished (to increasethe severity of the test), reweighed, and then subjected to the test for additional 4-hour periods in like manner. The results are given in the following table as: corrosion life, which indicates thenumber of hours required for the hearings to lose 1 00- mg. in weight, determined by interpolation of' the data obtained in the various periods.

Bearing Corrosion Life (Hrs.)

Oil or OilBlend Base Oil 9' Example 5' .-Laus'0n engine test A blend containing 1% by weight ofthe active ingredient of the. product of E xample 2 in a solvent extracted Mid -continent oil' of SAE 10 grade and a sample of the unblendedl baseoil were employed as the crankcase lubricant in tests with a Lauson engine operating at 295 F. jacket temperature: and: 300 oil temperature, 1800 R. PZ M. speed, and 1.5 indicated kilowattload, the tests being conducted for 25 hours each. The loss in weight of the copper-lead hearing was determined. The results of these observations are as follows:

Bearing Lubricant Weight Loss (in bearln Base Oil. 74 Base oil 1% product of Example 2 18 The products of the present invention may be employed not only in ordinary hydrocarbon lubricating oils but also in the heavy duty type of'lubricating oils which have been compounded with such detergent type additives as metalsoaps, metalpetloleum sulfonates; metal phenates, metal alcoholates, metal alkyl phenol sulfides, metal organ'ophosphates, phosphites', thiophosphates,

and thiophosphites, metal oxanthates and thioxanthates, metal thiocarbamates, and the like. Other types of additives, such as phenols and phenol sulfides, may also be present.

The lubricating oil base stock used in the compositions of this invention may be straight mineral lubricating oils or distillates derived from parafiinic, naphthenic, asphaltic or mixed base crudes, or, if desired, various blended oils may be employed as well as residuals, particularly those from which asphaltic constituents have been carefully removed. The oils may be refined by conventional methods using acid, alkali and/ or clay or other agents such as aluminum chloride, or they may be extracted oils produced by solvent extraction with solvents such as phenol, sulfur dioxide, etc. Hydrogenated oils or white oils may be employed as well as synthetic oils resembling petroleum oils, prepared, for example, by the polymerization of olefins or by the reaction of oxides of carbon with hydrogen or by the hydrogenation of coal or its products.

For the best results the base stock chosen should normally be an oil which with the new additive present gives the optimum performance in the service contemplated. However, since one advantage of the additives is that their use also makes feasible the employment of less satisfactory mineral oils, no strict rule can be laid down for the choice of the base stock. The additives are normally sufficiently soluble in the base stock, but in some cases auxiliary solvent agents may be used. The lubricating oils will usually range from about 40 to 150 seconds (Saybolt) viscosity at 210 F. The viscosity index may range from 0 to 100 or even higher.

Other agents than those which have been mentioned may be present in the oil composition, such as dyes, pour point depressants, heat thickened fatty oils, sulfurized fatty oils, sludge dispersers, antioxidants, thickeners, viscosity index improvers, oiliness agents, resins, rubber, olefin polymers, and the like.

Assisting agents which are particularly desirable as plasticizers and defoamers are the higher alcohols having preferably 8-20 carbon atoms, e. g., octyl alcohol, lauryl alcohol, stearyl alcohol, and the like.

In addition to being employed in lubricants, the additives of the present invention may also be used in other petroleum oil products such as motor fuels, heating oils, hydraulic fluids, torque converter fluids, cutting oils, flushing oils, turbine oils, transformer oils, industrial oils,

process oils, and the like, and generally as antioxidants in mineral oil products. They may also be used in gear lubricants, greases and other products containing mineral oils as ingredients.

What is claimed is:

1. A mineral oil containing dissolved therein a corrosion inhibiting amount of an oil-soluble compound of the formula wherein R is an aromatic radical having one alkyl group containing 4 to 24 carbon atoms; wherein x is an integer of from 1 to 2; wherein one of the symbols R R R and R represents a radical selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon radical containing from 1 to 4 carbon atoms, and a phenyl radical; and wherein the others of said symbols are hydrogen atoms.

2. The composition of claim 1 wherein said alkyl group contains from 6 to 12 carbon atoms.

3. The composition of claim 1 wherein one of said symbols is a phenyl radical.

4. The composition of claim 1 wherein said oil-soluble compounds is present in an amount in the range of 0.02 to 5.0 Wt. percent.

5. A mineral lubricating oil having a viscosity in the range of 40 to seconds (Saybolt) at 210 F. containing dissolved therein a corrosion inhibiting amount of an oil-soluble compound of the formula wherein R is an aromatic radical having one alkyl group containing 4 to 24 carbon atoms; wherein x is an integer of from 1 to 2; wherein one of the symbols R R R and R represents a radical selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon radical containing from 1 to 4 carbon atoms, and a phenyl radical; and wherein the others of said symbols are hydrogen atoms.

No references cited. 

1. A MINERAL OIL CONTAINING DISSOLVED THEREIN A CORROSION INHIBITING AMOUNT OF AN OIL-SOLUBLE COMPOUND OF THE FORMULA 